Heretofore, in the field of engines for automobiles and others, developments on an intake and exhaust system for increasing engine power output have been promoted.
For example, the following Patent Literature (PTL) 1 discloses an intake and exhaust system with a turbo supercharger (turbocharger), wherein the system comprises a plurality of independent exhaust passages connected to respective cylinders in a mutually independent manner, a collecting portion provided upstream of the turbocharger and at which the independent exhaust passages are merged together, and a valve provided in the collecting portion and capable of changing a cross-sectional area of each of the independent exhaust passages. In this system, when the cross-sectional areas of the independent exhaust passages is reduced by the valve, exhaust gas of a certain cylinder being in an exhaust stroke is ejected from an associated one of the independent exhaust passages into the collecting portion at relatively high speed, so that a so-called “ejector effect” can be expected in which a negative pressure generated around the ejected gas flow is applied to the remaining independent exhaust passages. Upon exerting the ejector effect, exhaust gas in the remaining independent exhaust passages is sucked toward a downstream direction, so that it becomes possible to increase an amount of gas to be supplied to the turbocharger, and thereby improve engine power output.